U.S. patent application number 12/473308 was filed with the patent office on 2009-12-03 for plant with piping mounted on branch pipe and boiling water reactor plant.
This patent application is currently assigned to Hitachi-GE Nuclear Energy, Ltd.. Invention is credited to Akitaka Hidaka, Masami Kato, Keita Okuyama, Shiro Takahashi.
Application Number | 20090296874 12/473308 |
Document ID | / |
Family ID | 41379810 |
Filed Date | 2009-12-03 |
United States Patent
Application |
20090296874 |
Kind Code |
A1 |
Okuyama; Keita ; et
al. |
December 3, 2009 |
Plant with Piping Mounted on Branch Pipe and Boiling Water Reactor
Plant
Abstract
A plant with piping mounted on branch pipe, wherein said piping
which introduces gas has a nozzle portion as a joint portion to a
vessel and a branch portion connected with a branch pipe; and
wherein an enlarged passage portion is formed at least at one of
said branch portion and said nozzle portion, and a passage
sectional area of said enlarged passage portion is larger than that
of said piping other than said enlarged passage portion. Since the
flow velocity of the gas flowing inside slows down at the enlarged
passage portion, the occurrence of acoustic resonance at the branch
portion or the nozzle portion can be suppressed. Accordingly, the
fluctuation pressure of the gas flowing in the piping can be
reduced even more.
Inventors: |
Okuyama; Keita; (Hitachi,
JP) ; Takahashi; Shiro; (Hitachi, JP) ; Kato;
Masami; (Hitachi, JP) ; Hidaka; Akitaka;
(Hitachinaka, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Assignee: |
Hitachi-GE Nuclear Energy,
Ltd.
|
Family ID: |
41379810 |
Appl. No.: |
12/473308 |
Filed: |
May 28, 2009 |
Current U.S.
Class: |
376/347 ;
137/599.01 |
Current CPC
Class: |
Y02E 30/30 20130101;
Y10T 137/87265 20150401; F16K 17/04 20130101; G21D 1/00 20130101;
Y02E 30/00 20130101 |
Class at
Publication: |
376/347 ;
137/599.01 |
International
Class: |
G21C 1/04 20060101
G21C001/04; F17D 3/00 20060101 F17D003/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 2008 |
JP |
2008-139262 |
Claims
1. A plant with piping mounted on branch pipe, wherein said piping
which introduces gas has a nozzle portion as a joint portion to a
vessel and a branch portion connected with a branch pipe; and
wherein an enlarged passage portion is formed at least at one of
said branch portion and said nozzle portion, and a passage
sectional area of said enlarged passage portion is larger than that
of said piping other than said enlarged passage portion.
2. The plant with piping mounted on branch pipe according to claim
1, wherein a center axis of said enlarged passage portion is in
alignment with a center axis of said piping at an upstream side and
a downstream side of said enlarged passage portion.
3. The plant with piping mounted on branch pipe according to claim
1, wherein said enlarged passage portion includes a plurality of
gas paths connected to said piping.
4. The plant with piping mounted on branch pipe according to claim
1, wherein said piping is steam pipes connected to a steam
generator.
5. The plant with piping mounted on branch pipe according to claim
1, wherein said plant is a reactor plant.
6. The plant with piping mounted on branch pipe according to claim
1, wherein said plant is a thermal power plant.
7. A boiling water reactor plant comprising: a nuclear reactor; and
a steam pipe having a nozzle part connected to said nuclear reactor
and introducing steam generated in said nuclear reactor, and a
branch portion connected with a branch pipe, wherein an enlarged
passage portion is formed at least at one of said branch portion
and said nozzle portion, and a passage sectional area of said
enlarged passage portion is larger than that of said steam pipe
other than said enlarged passage portion.
8. The boiling water reactor plant according to claim 7, wherein a
center axis of said enlarged passage portion is in alignment with a
center axis of said steam pipe at a downstream side of said
enlarged passage portion.
9. The boiling water reactor plant according to claim 7, wherein
said enlarged passage portion includes a plurality of steam paths
connected to said steam pipe.
10. The boiling water reactor plant according to claim 7, wherein
said branch pipe is a vent pipe with a steam safety relief valve.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese Patent
application serial no. 2008-139262, filed on May 28, 2008, the
content of which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] (Technical Field)
[0003] The present invention relates to a plant with piping mounted
on branch pipe and boiling water reactor plant.
[0004] (Background Art)
[0005] In the boiling water reactor plant (hereinafter referred to
as BWR plant) having the boiling water reactor (hereinafter
referred to as BWR) being a nuclear reactor, case examples have
been reported in which an increase in fluctuation pressure
accompanying an increase in main steam flow rate occurs when
capacity of electric power generation is increased, resulting in
damage to equipment in the BWR plant. Countermeasures such as
optimizing passage geometry and increasing structural strength for
the main steam system have been taken to avoid damaging the
equipment. Such case examples and countermeasures are disclosed in
G. Deboo, et al., "Quad cities unit 2 main steam line acoustic
source identification and load reduction", ICONE 14, (2006).
[0006] Acoustic resonance is thought to be a cause of the
fluctuation pressure in the main steam system such as the main
steam pipe. In the main steam system from a steam dome in a reactor
pressure vessel to a high-pressure turbine via the main steam pipe,
pressure waves due to the fluctuation pressure of the steam occur,
propagate, and reflect. In consequence, standing waves with a large
amplitude (acoustic resonance mode) may be formed and there is a
possibility that the amplitude of the fluctuation pressure is
increased. In particular, the BWR plants with increased capacity of
the electric power generation tend to cause the acoustic resonance
because of the large fluctuation pressure of the steam accompanying
the increase in the main steam flow rate.
[0007] As for the method for suppressing the acoustic resonance,
Japanese Patent Laid-open No. 2006-153869, for example, discloses a
method for suppressing the fluctuation pressure accompanying the
acoustic resonance occurring in the main steam system of the BWR
plant by use of a Helmholtz resonance tube. Japanese Patent
Laid-open No. 2008-14458 discloses a method for suppressing
fluctuation pressure accompanying the acoustic resonance by fitting
a canopy member to a cavity where the acoustic resonance is thought
to occur.
SUMMARY OF THE INVENTION
[0008] (Problem to be Solved by the Invention)
[0009] The inventors studied the occurrence of the acoustic
resonance in the BWR plant, and found out that the acoustic
resonance tends to occur at branch portions such as joint portions
between a vent pipe (branch pipe) and the main steam pipe where a
steam safety relief valve is installed.
[0010] According to Japanese Patent Laid-open No. 2006-153869, as
described above, when the Helmholtz resonance tube is installed in
the main steam pipe, the Helmholtz resonance tube can absorb
acoustic energy to effectively attenuate the acoustic resonance
mode. However, Japanese Patent Laid-open No. 2006-153869 does not
take countermeasures against the acoustic resonance occurring at
the joint portion between the vent pipe and the main steam pipe
where the steam safety relief valve is installed. By suppressing
the occurrence of the acoustic resonance at branch portions, the
fluctuation pressure in piping with branch portions can be reduced
even more.
[0011] Japanese Patent Laid-open No. 2008-14458, as with Japanese
Patent Laid-open No. 2006-153869, does not take countermeasures
against the acoustic resonance occurring at the branch portions of
piping such as the main steam pipe.
[0012] An object of the present invention is to provide a plant
with piping mounted on branch pipe and boiling water reactor plant
enabling even more reduced fluctuation pressure due to acoustic
resonance.
[0013] (Solution to Problem)
[0014] The present invention to accomplish the above object is
characterized in that in piping having a nozzle portion as a joint
portion to a vessel and a branch portion connected with a branch
pipe, and introducing gas through it, an enlarged passage portion
is formed at least at one of the branch portion and the nozzle
portion, and a passage sectional area of the enlarged passage
portion is larger than that of other portion of the piping.
[0015] Since the flow velocity of the gas flowing inside slows down
at the enlarged passage portion, the occurrence of acoustic
resonance at the branch portion or the nozzle portion can be
suppressed. Accordingly, the fluctuation pressure of the gas
flowing in the piping can be reduced even more.
[0016] (Advantageous Effects of Invention)
[0017] According to the present invention, the occurrence of
acoustic resonance at the branch portion or the nozzle portion can
be suppressed, and the fluctuation pressure of the gas flowing in
the piping can be reduced even more.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an enlarged longitudinal sectional diagram showing
a branch portion of a main steam pipe and a vent pipe shown in FIG.
2.
[0019] FIG. 2 is a structural diagram of a plant (a boiling water
reactor plant) with piping mounted on branch pipe of a first
embodiment which is a preferred embodiment of the present
invention.
[0020] FIG. 3 is a characteristic diagram showing a relationship
between St number and fluctuation pressure expressed as
root-mean-square (rms).
[0021] FIG. 4 is a structural diagram of a plant (a boiling water
reactor plant) with piping mounted on branch pipe of a second
embodiment which is another embodiment of the present
invention.
[0022] FIG. 5 is a structural diagram of a plant (a boiling water
reactor plant) with piping mounted on branch pipe of a third
embodiment which is still another embodiment of the present
invention.
[0023] FIG. 6 is a structural diagram of a plant (a boiling water
reactor plant) with piping mounted on branch pipe of a fourth
embodiment which is still another embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] An embodiment of the present invention is described
below.
First Embodiment
[0025] A plant with the piping mounted on branch pipe of a
preferred embodiment of the present invention is described below by
referring to FIG. 1 and FIG. 2. The plant with the piping mounted
on branch pipe of the present embodiment is a BWR plant 1. The BWR
plant 1 is provided with a nuclear reactor 2, a main steam pipe 10,
a turbine 12, a condenser (not shown), and a feed water pipe (not
shown).
[0026] The nuclear reactor 2 has a reactor pressure vessel 3
(hereinafter referred to as RPV) and a core placed in the RPV 3.
Numbers of fuel assemblies (not shown) are loaded in the core. A
removable cover 4 is attached to the RPV 3. In the RPV 3, a steam
separator (not shown) is placed above the core, and a steam dryer 5
with corrugated plates 6 is placed above the steam separator. The
main steam pipe 10 is connected to a nozzle 9 formed on the RPV 3,
and is communicated with a steam dome 7 formed above the steam
dryer 5 in the RPV 3. The turbine 12 is connected to the main steam
pipe 10. A vent pipe 15 is connected to the main steam pipe 10, and
a steam safety relief valve 13 is attached to the vent pipe 15. The
vent pipe 15 reaches a pressure suppression room placed in a
reactor containment vessel that surrounds the nuclear reactor 2,
and a fore-end portion of the vent pipe 15 is immersed in pool
water in the pressure suppression room (not shown). A joint portion
between the vent pipe 15 and the main steam pipe 10, in other
words, a branch portion 11 of the vent pipe 15 and the main steam
pipe 10 has larger passage sectional area (inner diameter) than
that of the main steam pipe 10 other than the branch portion 11.
The branch portion 11 of the main steam pipe 10 is enlarged larger
than the main steam pipe 10 other than the branch portion 11. The
branch portion 11 is an enlarged passage portion, and the vent pipe
15 is a branch pipe.
[0027] Cooling water in the RPV 3 is pressurized by driving a
recirculation pump (not shown) and is jetted from a nozzle of a jet
pump (not shown). The jetted cooling water flow sucks cooling water
around the nozzle into the jet pump and the joined cooling water is
discharged from the jet pump. The discharged cooling water is
supplied to the core. The heat generated by the nuclear fission of
nuclear fuel material in the fuel assemblies heats the cooling
water during the upward movement through the core, and part of the
heated cooling water becomes steam 16. The steam separator and the
steam dryer 5 remove moisture contained in the steam 16. The steam
16, from which the moisture has been removed, is introduced to the
turbine 12 through the main steam pipe 10, and rotates the turbine
12. A generator (not shown) coupled to the turbine 12 is rotated,
and generates electric power. The steam 16 exhausted from the
turbine 12 is condensed in a condenser (not shown) to become water.
The water is pressurized by a feed pump (not shown) and is supplied
into the RPV 3 as feed water through the feed water pipe (not
shown). The nuclear reactor 2 of the BWR plant is a steam
generator. The moisture separated in the steam dryer 5 is
discharged into a region formed below the steam dryer 5 and between
the steam separators through a drain pipe 8.
[0028] If the inner pressure of the RPV 3 was to rise above a set
value, the steam safety relief valve 13 automatically opens. In
other words, the valve disc 17 of the steam safety relief valve 13
is pushed up. The steam 16 in the RPV 3 is emitted into the pool
water in the pressure suppression room through the main steam pipe
10 and the steam safety valve 13, and the steam 16 is condensed
with the pool water. The inner pressure of the RPV 3 is, therefore,
suppressed lower than the set value, and the safety of the nuclear
reactor 2 is secured.
[0029] In the normal operation of the BWR plant 1, the flow
velocity of the steam 16 introduced to the turbine 12 slows down in
the branch portion 11 where the passage sectional area increases.
If the flow rate of the steam 16 flowing in the main steam pipe 10
is constant, the flow velocity of the steam 16 in the branch
portion 11 gets smaller in reverse proportion to the squared inner
diameter of the branch portion 11.
[0030] The fluctuation pressure occurring at the branch portion 11
accompanying the acoustic resonance caused by the flow of the steam
16 is represented by Equation (1) with a dimensionless number
called the Strouhal number (St):
St=f.times.d/U (1)
[0031] where d is a diameter of the main steam safety relief valve
13, U (m/S) is flow velocity of the steam 16 at the branch portion
11, and f is frequency (s.sup.-1) of the fluctuation pressure
accompanying the acoustic resonance occurring at the branch portion
11. The frequency f is represented by Equation (2):
f=c/(4L) (2)
[0032] where c is speed (m/S) of sound of the steam 16 flowing in
the branch portion, and L is a length (m) of the main steam safety
relief valve 13. In other words, the flow velocity of the steam 16
at the branch portion 11 is in a reverse proportion relation to the
St number.
[0033] A profile of root-mean-square (rms) that expresses the
degree of the fluctuation pressure at the branch portion 11 of the
present embodiment versus the St number is shown in FIG. 3. When
the reactor power (electric generating power) of the BWR plant 1 is
increased, the core flow rate (flow rate of cooling water supplied
to the core) is increased, thereby leading to an increase in the
flow rate of the main steam. In the present embodiment, since the
passage sectional area of the main steam pipe 10 is enlarged at the
branch portion 11, the flow velocity of the steam 16 flowing in the
branch portion 11 slows down, and the fluctuation pressure
occurring at the branch portion 11 decreases (region B). The
decrease in the fluctuation pressure is brought about by the
suppression of the occurrence of acoustic resonance at the branch
portion 11 due to the reduced flow velocity of the steam 16 because
of the enlargement of the passage sectional area at the branch
portion 11.
[0034] In the conventional BWR plant where the passage sectional
area of the branch portion is the same as the portions other than
the main steam pipe 10 and a Helmholtz resonance tube is not
installed, since the flow velocity of the steam 16 at the branch
portion becomes faster than that of the present embodiment, the
fluctuation pressure may increase like region A shown in FIG. 3. In
contrast, in the present embodiment, since the passage sectional
area of the branch portion 11 is larger than that of the steam pipe
10 other than the branch portion 11, the occurrence of acoustic
resonance is suppressed and the fluctuation pressure is reduced
when compared with the conventional BWR plant.
[0035] The reason why the present embodiment can suppress the
occurrence of acoustic resonance in this way is described below. By
forming the enlarged passage portion, if the flow rate of the steam
flowing in the main steam pipe 10 does not change, the linear flow
velocity is reduced in the enlarged passage portion. For this
reason, the fluctuation pressure is reduced like region B shown in
FIG. 3. In the meantime, at the branch portion of the main steam
pipe 10 and the vent pipe 15, vortexes occur in the steam flow. If
the period of vortex generation comes close to the natural
frequency peculiar to the configuration of the equipment of the BWR
plant 1, sounds generated by the vortexes are intensified. This
phenomenon is called acoustic resonance. When the flow velocity of
the steam is slowed down by forming the enlarged passage portion
(branch portion 11 having the passage sectional area that is larger
than that of the steam pipe 10 except the branch portion 11) like
the present embodiment, the period of the vortex generation
generated at the branch portion 11 of the main steam pipe 10 and
the vent pipe 15 becomes longer, and the period of the vortex
generation departs from the natural frequency described above.
Accordingly, the occurrence of fluctuation pressure is reduced.
[0036] When the enlarged passage portion is formed at the
downstream side of the branch portion 11 of the main steam pipe 10
and the vent pipe 15, the occurrence of acoustic resonance at the
branch portion 11 cannot be suppressed. The reason why the
occurrence of acoustic resonance is not suppressed is that even if
the enlarged passage portion is formed at the downstream side, the
vortexes are generated at the branch portion and the flow velocity
of the steam is not slowed down at the branch portion, the period
of the vortex generation does not depart from the natural frequency
described above.
[0037] In a BWR plant of which the main steam pipe is equipped with
a Helmholtz resonance tube, described in Japanese Patent Laid-open
No. 2006-153869, since the Helmholtz resonance tube is installed,
the occurrence of acoustic resonance is suppressed and the peak
value of the fluctuation pressure is reduced when compared with the
conventional BWR plant described above, wherein the passage
sectional area of the branch portion of the steam pipe 10 is the
same as that of other portion of the main steam pipe 10 and the
Helmholtz resonance tube is not installed. However, in the BWR
plant described in Japanese Patent Laid-open No. 2006-153869, the
passage sectional area of the branch portion to which the vent tube
is connected is the same as that of other portion of the main steam
pipe 10, that is to say, the branch portion with an enlarged
passage sectional area is not formed, the flow velocity of the
steam 16 at the branch portion is not slowed down. Consequently, in
the region where the flow velocity of the steam 16 is faster than
that in region B shown in FIG. 3, the peak of the fluctuation
pressure described above occurs. In the BWR plant described in
Japanese Patent Laid-open No. 2006-153869, the peak value of the
fluctuation pressure caused by the acoustic resonance becomes
larger than the fluctuation pressure of the present embodiment in
region B. The fluctuation pressure in the present embodiment is
reduced more than that in Japanese Patent Laid-open No.
2006-153869.
[0038] In the present embodiment, a center axis of the branch
portion 11 of which the passage sectional area is enlarged is in
alignment with the center axis of the main steam pipe 10 at the
upstream side and the downstream side of the branch portion 11. For
this reason, the occurrence of acoustic resonance at the branch
portion 11 can be effectively suppressed. Even when the center axis
of the branch portion 11 is not in alignment with the center axis
of the main steam pipe 10 at the upstream side and the downstream
side of the branch portion 11, the fluctuation pressure of the
steam 16 is reduced more than that in Japanese Patent Laid-open No.
2006-153869, but when these center axes are aligned, the
fluctuation pressure of the steam 16 can be further reduced.
[0039] In the present embodiment, since the occurrence of acoustic
resonance at the branch portion 11 can be suppressed to reduce the
fluctuation pressure of the steam 16 flowing in the main steam pipe
10, a power uprate of the BWR plant 1 can easily be accomplished.
The power uprate of the BWR plant 1 is performed in such a way that
the core flow rate is increased, thereby increasing the reactor
power over the rated power (100% power). In the power uprate, the
flow rate of the steam supplied to the turbine 12 is increased. In
the present embodiment, since the occurrence of acoustic resonance
at the branch portion 11 can be suppressed by forming the enlarged
passage portion at the branch portion 11 to reduce the fluctuation
pressure of the steam 16 flowing in the main steam pipe, the flow
rate of the steam 16 supplied to the turbine 12 can easily be
increased. Consequently, the present embodiment can easily
accomplish the power uprate of the BWR plant 1.
[0040] In the present embodiment, since the enlarged passage
portion is formed at the branch portion 11, the reactor building
needs not to be enlarged.
Second Embodiment
[0041] A plant with the piping mounted on branch pipe of another
embodiment of the present invention is described below by referring
to FIG. 4. The plant with the piping mounted on branch pipe of the
present embodiment is a BWR plant 1A. The BWR plant 1A is comprised
of a nuclear reactor 2, a main steam pipe 10A, a turbine 12, a
condenser (not shown), and a feed water pipe (not shown). In the
BWR plant 1A of the present embodiment, an enlarged passage portion
is formed at a nozzle 9A formed on a RPV 3 and located upstream of
a joint portion between the main steam pipe 10A and a vent pipe. In
the present embodiment, the nozzle 9A is a part of the main steam
pipe 10A. The BWR plant 1A has the same structure as that of the
BWR plant 1 except that the enlarged passage portion is formed not
at a branch portion 11 but at the nozzle 9A. The inner diameter of
the nozzle 9A is larger than that of the main steam pipe 10A other
than the nozzle 9A.
[0042] Since the passage sectional area of the nozzle 9A of the
main steam pipe 10A is larger than that of the main steam pipe 10A
other than the nozzle 9A, the present embodiment can obtain the
same effect as that of the first embodiment. In other words, the
occurrence of acoustic resonance at a joint portion between a vent
pipe 15 and the main steam pipe 10A (the branch portion of the main
steam pipe 10A) can be suppressed, and the fluctuation pressure of
the steam 16 is reduced more than that in Japanese Patent Laid-open
No. 2006-153869. It is also not needed for the present embodiment
where the enlarged passage portion is formed at the nozzle 9A to
increase the size of a reactor building.
[0043] The reason why the present embodiment can suppress the
acoustic resonance at the nozzle 9A is as follows. In the nozzle 9
(first embodiment) where the enlarged passage portion is not
formed, since the steam flow exhausted from the RPV 3 is rapidly
narrowed down, that is to say, becomes contracted, the fluctuation
pressure that turns into sound occurs at the nozzle 9. In contrast,
in the present embodiment, the contraction effect at the nozzle 9A
can be reduced by gradually changing the passage sectional area of
the nozzle 9A down to the main steam pipe 10A downstream of the
nozzle 9A. For this reason, the fluctuation pressure of the steam
that turns into sound at the nozzle 9A can be suppressed.
[0044] In the present embodiment, the enlarged passage portion
formed in the first embodiment can be, further, formed at the
branch portion of the steam pipe 10A and the vent pipe 15. Since
the flow velocity of the steam can be slowed down at the nozzle 9A
and the branch portion, the fluctuation pressure of the steam
flowing in the main steam pipe 10A can be reduced more than in the
first embodiment.
Third Embodiment
[0045] A plant with the piping mounted on branch pipe of another
embodiment of the present invention is described below by referring
to FIG. 5. The plant with the piping mounted on branch pipe of the
present embodiment is a BWR plant 1B. The BWR plant 1B is,
similarly to the BWR plant 1, comprised of a nuclear reactor 2, a
main steam pipe 10, a turbine 12, a condenser (not shown), and a
feed water pipe (not shown). In some BWR plants, a branch pipe 18
of which one end is sealed off is connected to the main steam pipe
10. In the BWR plant 1B of the present embodiment, the main steam
pipe 10 is equipped with a branch pipe 18. An inner diameter of a
joint portion between the main steam pipe 10 and the branch pipe
18, that is to say, a branch portion (an enlarged passage portion)
19 is larger than that of the main steam pipe 10 other than the
branch portion 19. The passage sectional area of the branch portion
19 is larger than that of the main steam pipe 10 other than the
branch portion 19.
[0046] The flow velocity of the steam 16 flowing in the main steam
pipe 10 slows down in the branch portion 19. For this reason, in
the present embodiment, the acoustic resonance at the branch
portion 19 of the main steam pipe 10 and the branch pipe 18 can be
suppressed, and the fluctuation pressure of the steam 16 can be
reduced as with the first embodiment.
[0047] The branch pipe 18 is located downstream of a branch portion
11 (not shown) of a vent pipe 15 (not shown) and the main steam
pipe 10. Since the passage sectional area of the branch portion 11
is, similarly to the first embodiment, enlarged, the occurrence of
acoustic resonance at the branch portion 11 of the vent pipe 15 and
the main steam pipe is suppressed.
Fourth Embodiment
[0048] A plant with the piping mounted on branch pipe of another
embodiment of the present invention is described below by referring
to FIG. 6. The plant with the piping mounted on branch pipe of the
present embodiment is a BWR plant 1C. The BWR plant 1C is,
similarly to the BWR plant 1, provided with a nuclear reactor 2, a
main steam pipe 10, a turbine 12, a condenser (not shown), and a
feed water pipe (not shown). In the BWR plant 1C of the present
embodiment, the main steam pipe 10 at the branch portion of the
vent pipe 15 is comprised of two steam paths 20A and 20B instead of
the branch portion 11 formed in the first embodiment. A vent pipe
15 to which a steam safety relief valve 13 is attached is connected
to the steam path 20A. The steam paths 20A and 20B are connected to
the main steam pipe 10 upstream of the branch portion of the vent
pipe 15 and the steam path 20A, and are also connected to the main
steam pipe 10 downstream of the branch portion. The steam paths 20A
and 20B are connected to the main steam pipe 10 upstream and
downstream of the branch portion with a same tilt angle to avoid an
increase in pressure loss. The inner diameter of each of the steam
paths 20A and 20B is the same as the inner diameter of the main
steam pipe 10. The passage sectional area of the main steam pipe 10
at the branch portion of the vent pipe 15 and the steam path 20A is
doubled by the installation of the steam paths 20A and 20B. The
installation of the steam paths 20A and 20B provides the same
function as forming the branch portion 11 of the first embodiment
to the branch portion of the vent pipe 15 and the steam path 20A
(the branch portion of the vent pipe 15 and the main steam pipe
10). In other words, since the flow velocity of the steam slows
down at the steam paths 20A and 20B, the occurrence of acoustic
resonance is suppressed at the branch portion of the vent pipe 15
and the steam path 20A and the fluctuation pressure of the steam 16
is reduced.
[0049] In the present embodiment, since the plurality of steam
paths (such as the steam paths 20A and 20B) are formed at a part of
the main steam pipe 10 such as the branch portion of the vent pipe
15 and the main steam pipe 10, it is not needed to increase the
size of the reactor building.
[0050] In the third embodiment, as with the present embodiment, the
branch portion 19 can be comprised of a plurality of steam
paths.
[0051] Each embodiment described above is applicable to a plant
having piping mounted on branch pipe with gas (steam, air, etc.)
flowing inside such as a pressurized water reactor plant with a
steam pipe connecting a steam generator with a turbine, and a
thermal power plant with a steam pipe connecting a boiler with a
turbine. Each embodiment described above is also applicable to a
space heating system with a steam pipe connected to a steam
generator.
* * * * *